Current Electricity

🚗 Sec 4 NA Combined Physics R e s h a r e Document Style C u r r en t E l ec t r i c i t y 1 / 1 Add Source Science Secondary 4 Physics The direction of the flow of electrons is from the negative terminal to the positive terminal. The flow of electric current is in the direction opposite to that of the flow of electrons. Like electrons charges repel each other (for example, an electron has a negative charge and another electron has a negative charge, so they both will repel) Likewise, opposing poles attract, just like a magnet 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 1/11

Flow of Electricity through a Circuit | Electricity and Circuits | Don't Memor ise YouTube The negative terminal of the cell repels the electrons near it, and the electrons which get repelled go in the downwards direction Electron flow is from negative to positive end of the battery and direction of current is from positive to negative ends of the battery The formula of electric current is I = Q / t Where, I Charge, Q Current and t = time The S.I Unit of Current is Ampere A S o , h o w d i d a c o n v en t i o n a l c u r r en t g et i t s n a m e? Before the discovery of electrons, scientists believed that electric current was caused by the movement of positive charges. Although this idea was later proven wrong, the idea remains. This ‘movement ’ of positive charges is called conventional current. Electric current is actually caused by the flow of electrons from the negative terminal to the positive terminal. Ho w d o w e m ea s u r e c u r r en t s ? 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 2/11

An ammeter is used to measure current It should be connected in series to the circuit 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 3/11

O p en a n d c l o s ed c i r c u i t s An open circuit is a circuit in which current is unable to flow due to breaks in the circuit 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 4/11

A closed circuit allows electricity to flow through without any interruptions (but in this diagram, the bulb will not light up due to the least resistance being on the bypass) E l ec t r o m o t i v e F o r c e a n d P o t en t i a l D i f f er en c e The electromotive force (e.m.f) of an electrical energy source is defined as the work done by the source in driving a unit charge around a complete circuit. 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 5/11

Formula where ε = e.m.f. of electrical energy source; W work done (amount of non-electrical energy conver ted to electrical energy); Q amount of charge. The SI unit of e.m.f is the j o u l e p er c o u l o m b (J C 1 ) or v o l t (V ). So, e.m.f is basically volt! Ho w d o w e m ea s u r e e. m . f ? We make use of a voltmeter to measure volt, which is the SI unit of e.m.f S er i es a n d P a r a l l el a r r a n g em en t 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 6/11

In series, e.m.f resultant is equal to e.m.f 1 emf 2 ... In parallel, e.m.f resultant is equal to e.m.f 1 e.m.f 2 ... P o t en t i a l D i f f er en c e What is the main difference between Potential difference and Electromotive Force? (underlined) The potential difference (p.d.) across a component in an electric circuit is the work done to drive a unit charge through the component. The electromotive force (e.m.f) of an electrical energy source is defined as the work done by the source in driving a unit charge around a complete circuit. Formula 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 7/11

where V p.d. across a component; W work done (amount of electrical energy conver ted to other forms); Q amount of charge. The SI unit of potential difference is the v o l t (V ). *Ammeter should be connected to the circuit in series and voltmeter is connected in parallel to the circuit 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 8/11

What is the answer to this question? T h e a n s w e r i s A a n d C R es i s t a n c e The resistance of a component is the r a t i o of the p o t en t i a l d i f f er en c e across the component to the c u r r en t flowing through the component. The higher the resistance is, the more difficult it is for the current to flow. Formula R = V / I where R resistance of a component; V p.d. across a component; I current flowing through component. The SI unit of resistance is the o h m (Ω ). W h a t a r e R es i s t o r s ? A resistor is a conductor in a circuit that is used to control the size of the current flowing in a circuit. There are two types of resistors — f i x ed resistors and v a r i a b l e resistors (or rheostats). 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 9/11

R es i s t i vi t y f o r m u l a ρ = R A / l where ρ = resistivity of conductor; R resistance of conductor; A cross-sectional area of conductor; l = length of conductor. The SI unit of resistivity is the o h m m et r e (Ω m ). R es i s t i vi t y is a proper ty of the material and it is i n d ep en d en t of the dimensions of the material. Current Electricity TableFilter Sor t Silver 1.6 10^6 Copper 1.7 10^8 Tungsten 5.5 10^8 Iron 9.8 10^8 Constantan 49 10^8 Nichrome 100 10^8 Graphite 3000 10^8 Polythylene about 10^16 M a t e r i a l R e s i s t i vi t y R e s i s t i vi t y o f M a t e r i a l s ( N … 2/22/25, 10:38 AM Current Electricity https://www.remnote.com/w/63c4983acdbac42fbe812c31/Current-Electricity-XQUC1bBd5ZwcZMh1U 10/11